Cathode ray tubes



Aug.'12, 1969 K. E. FLETCHER ETAL 3,460,879

CATHODE RAY TUBES Filed'June 26. 1967 INVENTORS ALFRED 5. Con A KENNETH E. Herc/me.

XML/6m ATTORNEY United States Patent 3,460,879 CATHODE RAY TUBES Kenneth E. Fletcher and Alfred E. Cole, London, England, assignors to Thorn-AEI Radio Valves & Tubes Limited, London, England Filed June 26, 1967, Ser. No. 648,879 Claims priority, application Great Britain, June 29, 1966, 29,248/ 66 Int. Cl. H01j 9/18, 9/00; H05k 5/00 US. Cl. 316-19 2 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the manufacture of cathode ray tubes.

The method of manufacture most commonly employed at present comprises sealing a stem carrying the electron gun of the tube to the bulb of the tube and coupling an exhaust tubulation provided on the stem to exhaust equipment by means of an O-ring seal. After completion of the exhaust temperature-cycling and cathode activation, the tube is removed from the exhaust unit by sealing off the exhaust tubulation.

This method has the disadvantage that the pumping speed of the exhaust equipment is severely limited by the size of the exhaust tubulation, this disadvantage increasing as the diameter of the tubulation decreases. Another disadvantage, arising particularly with small cathode ray tubes, is that the fragility of the tubulation increases as the size of the tubulation decreases.

According to the present invention there is provided a method of manufacturing a cathode ray tube comprising the steps of arranging the open end of the neck of the tube and a stem carrying the electron gun of the tube within an evacuable chamber, the neck being temporarily sealed in a gas-tight manner through the wall of the chamber, evacuating the chamber and thereby also evacuating the envelope of the cathode ray tube through the neck While thermal processing of the tube is carried out, producing relative movement between the stem and the neck to bring these into engagement with one another, forming a permanent seal between the stem and the neck, and removing the cathode ray tube from the chamber.

The invention also provides a cathode ray tube having an evacuated envelope comprising a bulb portion, a neck portion extending from the bulb portion and a stem portion sealed to the neck portion and supporting an electron gun structure, no exhaust tubulation being provided.

The invention will be described, by way of example, with reference to the accompanying diagrammatic drawing in which- FIG. 1 is a view of part of the neck of a cathode ray tube and a stem to be sealed thereto and part of an evacuable chamber in which the sealing is to take place,

3,460,879 Patented Aug. 12, 1969 FIG. 2 is an enlarged view in section of part of the stem shown in FIG. 1, and

FIG. 3 is a view similar to that of FIG. 1 showing the neck and stem in position to be sealed together.

Referring to the drawing, the outer end of the neck 10 of a cathode ray tube is sealed, by means of an O-ring 11 through a wall 12 of a chamber 13 capable of being evacuated. The bulb 20 of the cathode ray tube is located above the wall 12. A stem 14 carrying the electron gun (not shown) and the usual terminals 15, as shown in FIG. 2, is mounted upon a support 16 within the evacuable chamber 13. Means, not shown, are provided for moving the support 16 carrying the stem 14 in the directions of the arrows 17. The stem is provided around its periphery with a ring 18 of glass frit or solder.

When the parts are in position as described, the chamber 13 is evacuated and the cathode ray tube bulb 20 is therefore evacuated through the neck 10. The evacuation process may be as at present excepting that the evacuation itself takes place through the neck 10, no exhaust tubulation being required.

An electric oven 19 surrounding the neck 10 and stem 14 is then switched on and when the frit or solder 18 has melted, the support 16 and stem 14 are raised to the position shown in FIG. 3 where the stem is properly located to cap the tube neck. The oven 19 is then switched off and the setting frit or solder 18 forms a seal between neck and stem. The neck 10 with the stem 14 sealed thereto can then be withdrawn upward through the O-ring seal 11.

A suitable glass frit 18 is Corning thermal setting solder glass 7576 in a binder formed of 1% nitrocellulose in amyl acetate.

The support 16 may be moved by any convenient means such for example as electromagnetic means.

What is claimed is:

1. A method of manufacturing a cathode ray tube having an envelope whereof the neck of the bulb portion has an electron gun structure positioned therein supported on a stem sealed thereto, said method comprising the steps of arranging the open end of said neck and said stem within an evacuable chamber, said neck protruding thereinto through a compatible opening in the Wall of said chamber with said bulb portion being externally positioned relative to said chamber, said stern being positioned on movable support means aligned with the open end of said neck;

temporarily clamping said neck in a gas-tight manner at said wall opening to achieve said aligned positioning; evacuating said chamber and the envelope of the cathode ray tube opening thereinto, said envelope being evacuated through the open neck thereof;

thermally processing said tube while said evacuation is in process;

moving said stern support means to fully position said associated electron gun within said neck and bring said stem into engagement with the open end of said neck;

forming a seal between said neck and stem portions to provide a permanent closure for said tube; and removing said sealed neck portion of said cathode ray tube from said chamber.

2. The method according to claim 1 wherein the stem portion has a ring of glass frit provided around its References Cited UNITED STATES PATENTS 3,147,053 9/1964 Phelps et al. 316--19 3,331,979 7/1967 Sybeldon et a1. 31364 FOREIGN PATENTS 2/ 1955 Great Britain.

LEWIS H. MYERS, Primary Examiner 5 D. A. TONE, Assistant Examiner US. Cl. X.R. 

